PITTSBURGH, June 29 -- Much of the focus will be on the Washington Nationals' bullpen, because Saul Rivera couldn't hold a two-run lead in the seventh inning, then Jon Rauch couldn't find the plate in the ninth, the key elements in what became a 3-2 loss to the Pittsburgh Pirates on Friday night.

But when pinch runner Jose Castillo slid home with the game-winner on Jose Bautista's sacrifice fly in the bottom of the ninth, Ryan Zimmerman was among the Nationals who slumped toward the dugout, well aware his club has now lost four in a row and 10 of 13. The Nationals' offense has all but evaporated, and their would-be star of a third baseman heads toward the all-star break scratching and kicking just to stay afloat.

"I'm fine," Zimmerman said in the quiet of the visitors' clubhouse at PNC Park, an 0-for-4 night behind him.

That is the Nationals' standard response about Zimmerman. He is fine. He will be better. Don't worry. And perhaps, as his average dropped to .241 after 11 straight at-bats without a hit, it is worth a refresher course. He is 22 years old. Two years ago, he was a college junior. He is being asked to hit third on what, statistically, is the worst offensive club in baseball. With first baseman Dmitri Young -- who went 2 for 4 Friday -- the only consistent hitter, there is nowhere for Zimmerman to hide, particularly during a 14-game stretch in which the team is averaging 2.7 runs.

"I think a lot of us forget," Manager Manny Acta said, "that this kid is just learning how to play the game up here."

The lessons over the first half of the season have been difficult. Friday, the Nationals came up against Pirates right-hander Ian Snell, who is quietly putting together one of the best seasons in the National League. Snell struck out Zimmerman on three pitches in the first inning, got him to ground out hard to second in the fourth, then struck him out on a slider out of the zone in the seventh. Quick work each time.

That is not the kind of performance the slumping Nationals need, and Zimmerman knows it. The expectations on him -- after a rookie season in which he hit .287 and drove in 110 runs, stroking 47 doubles along the way -- were enormous, particularly because he is the focus of a full-on rebuilding effort. In his second season, he has been anointed the guy around whom the lineup turns.

"I feel like I'm ready to be that guy," Zimmerman said. "We still have a lot of season left to where I still can be that guy. It's been tough. Pitchers have been tough on me. They bear down on me. I'm learning as I go."

Learning at the major league level, though, comes with a bit of a spotlight. As Acta said Friday, "He doesn't know everything."

"People are waiting for him to hit 30 and knock in 120," right fielder Austin Kearns said. "It's not that easy. He can do it, but it's not easy."

Nor is scoring, at least for the Nationals. They took a 2-0 lead on Snell on the strength of Ryan Langerhans's solo homer in the third and Felipe Lopez's sacrifice fly in the seventh. Rookie left-hander Matt Chico -- who admitted that he "got away with a lot" in a six-inning, no-run outing -- was poised to post his first win since May 17.

But then, disaster. Rivera walked the first man he faced in the seventh, eighth-place hitter Jack Wilson, on four pitches. "It hurt," Rivera said, "big-time."

Particularly when pinch hitter Nate McLouth hit Rivera's sixth pitch -- and first strike -- for a triple to right-center. An out later, Bautista tied it with a sacrifice fly. The Nationals' best chance to win -- behind their bullpen -- had evaporated.

"We had it," Acta said. "We were leading. I take my chances every day with our bullpen."

But Acta knows, too, that his bullpen couldn't produce more runs. After Young's single off Snell in the seventh, the Nationals failed to collect another hit. Rauch, then, pitched a perfect eighth -- extending a scoreless-innings streak to 12 1/3 -- and was asked to come out for the ninth. The inning: Single, sacrifice, wild pitch on a change-up in the dirt, intentional walk, unintentional walk, game-ending sacrifice fly.

"I just had an off night," Rauch said. "It happens. Plain and simple, that's the easiest way to explain it."

Zimmerman, too, could explain his night in the same way. But it was one of many. His demeanor in the clubhouse seems steady. "He has the makeup of somebody who's going to be around a long time," Young said.

But behind that steely facade, there are glimpses of frustration. A few more bats thrown at the ground after popups. A few more words uttered into his glove.

"To be 22 and doing what he's doing, and what's expected of him, you have to have your head on right," Kearns said. "He expects a lot of himself. I think we all see that and know that he doesn't just take it in stride if he's not doing what he's capable of doing."

Zimmerman figures he is capable of being the guy he is expected to be. His power numbers -- 12 homers and 42 RBI -- are decent, and they lead the team. His on-base percentage, down from .351 a year ago to .292, is not.

"It seems like if I try and be more selective and work the count," he said, "all of a sudden the pitcher's up 1-2 or 0-1 or something, and I'm in a hole. It's tough."

For half a season, it has been. But whether the Nationals are scoring or they're not, whether they're winning or losing, whether he is hitting or he isn't, Zimmerman will be in the lineup batting third.

"For most of us, it's a game of adjustments," Kearns said. "He'll adjust, and he'll be fine."